Hi,
I am a Vet Tech, and unfortunately run across Lyme disease all the time. An animal can become infected, yet not be symptomatic for several months to a year! There are also a couple other tick-borne diseases that our little friends can get (namely, Anaplasmosis and Erhlichiasis among others). Anaplasma and Lyme are both transmitted from a deer tick, but Erhlichia is not, so you should be aware of all ticks found on your pet. Your vet may have an in-house test called a 4DX that tests for heartworm, lyme, anaplasma and erhlichia and luckily it is a very quick, quite accurate 10 minute test. However, it can take up to 6 weeks for a positive test to appear (i.e. Fluffy may have gotten Lyme, but the test would not show up as such for several weeks after).
As purple mentioned, extreme lameness is often the most recognizable symptom. Also, keep an eye on her behaviour, appetite, drinking habits etc and make note of anything out of norm. If you are concerned, feel free to call your vet and inform him/her that you did find a couple of ticks and to schedule a time in the future to test for such diseases.
You don't need to be afraid of the consequences of contracting dick-borne diseases, as if they are caught and treated (with antibiotics), everything should be just fine. Of note, my dog was just diagnosed with Lyme, and she showed no symptom that we recognized at the time. In retrospect, last summer she was acting off, not wanting to run or swim as much, and we had attributed it to her getting old. She is doing just fine on the antibiotics. Keep in mind that untreated, those diseases can lead to a host of other problems, so a yearly screen for them is ideal to catch any while they are not an issue.
The Lyme vaccine does not prevent lyme disease. It does, however, lower the chances of contracting it and, should your dog get it, the symptoms will be less severe (just like Frontline, which is a great product, isn't foolproof. Sometimes those little buggers get through). You are doing great! Just think, I have a client who does not use FL, and she takes 15-20 ticks off PER DAY from her dogs, and her family has had to be treated several times as humans can also contract Lyme.
Sorry for being long-winded, and I hope I didn't end up confusing you more. If you have any further questions or concerns, I'd recommend you contact your vet to have them addressed.
Take care!
